. Damping-off in forest nurseries. Plant diseases; Trees. UNITED STATES DEPARTMENT OF AGRICULTURE fe BULLETIN No. 934 $fjy|. s^jtrs&ju Contribution from the Bureau of Plant Industry \VM. A. TAYLOR, Chief Washington, D. C. PROFESSIONAL PAPER June 16, 1921 DAMPING-OFF IN FOREST NURSERIES. By Cabl II\i:tm'. formerly Pathologist, Office of Investigations in Forest Pathology. CONTENTS. Page. Damping-off in general 1 Damping-off of conifers 7 Causal fungi 27 Corticium vagum -7 Fusarium spp , 34 Pythium debaryanum 35 Rheospora ngi am aphanider- ma tus 55 Phytophthora spp 59 Miscellaneous phycomj
. Damping-off in forest nurseries. Plant diseases; Trees. UNITED STATES DEPARTMENT OF AGRICULTURE fe BULLETIN No. 934 $fjy|. s^jtrs&ju Contribution from the Bureau of Plant Industry \VM. A. TAYLOR, Chief Washington, D. C. PROFESSIONAL PAPER June 16, 1921 DAMPING-OFF IN FOREST NURSERIES. By Cabl II\i:tm'. formerly Pathologist, Office of Investigations in Forest Pathology. CONTENTS. Page. Damping-off in general 1 Damping-off of conifers 7 Causal fungi 27 Corticium vagum -7 Fusarium spp , 34 Pythium debaryanum 35 Rheospora ngi am aphanider- ma tus 55 Phytophthora spp 59 Miscellaneous phycomj cil Other fungi , 64 Relative importance of the damping- off fvinsi on conifers 65 Page. Damping-off fungi as causes of root- rot and late damping-off 70 Relation of environmental factors to damping-off 7-". Density of sowing 74 Moisture and temperature factors-- 7.~> Chemical factors-. 70 Biologic factors 82 Acknowledgments S6 Summary ' S6 Literature cited 91 DAMPING-OFF IN GENERAL. Damping-off is the commonest English name for a symptomatic .rmip of diseases affecting great numbers of plant species of widely separated phylogenetic groups. It is commonly used for any disease which results in the rapid decay of young succulent seedlings or soft cuttings. Young shoots from underground rootstocks may also be damped-off before they break through the soil (Go).1 The same term is even used for diseases affecting the prothallia of vascular crypto- gams (2). The name apparently originated in the fact that the dis- ease is usually m<»t prevalent under excessively moist conditions. In those cases in which the disease becomes serious without the pres- ence of unusual amounts of moisture the term is a misnomer. It is, however, so thoroughly established in practical use that it would be impossible, even if desirable, to establish any other name. 1 The serial numbers in parentheses refer to " Literature cited," at the end of this bulletin. 19651°—Bull. 934—2] 1
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